Heretofore, as an article having releasability on its surface, a protective material for an adhesive face of repositional notes, pressure-sensitive adhesive sheets or tapes, a release film, a release paper and the like have been known. As a method of imparting releasability to the surface of an article, a method of treating the surface of an article with e.g. a silicone type or fluorine type release agent composition has been known. However, with respect to a silicone type release agent, a silicone compound forming a release layer is usually easily attached to a substrate, such being problematic when bonding and separation are repeatedly carried out. On the other hand, as a fluorine type release agent, a release agent composition having e.g. a phosphate compound having a polyfluoroalkyl group (hereinafter a polyfluoroalkyl group will be referred to as a Rf group) having at least 8 carbon atoms dissolved or dispersed in a medium has been known. Further, a release agent composition comprising a copolymer of an acrylate having a C5-18 alicyclic group and an acrylate having a perfluoroalkyl group having at least 8 carbon atoms has also been known (Patent Document 1).
However, in recent years, EPA (United States Environmental Protection Agency) has pointed out that a compound having a perfluoroalkyl group (hereinafter a perfluoroalkyl group will be referred to as a RF group) having at least 8 carbon atoms has a high environmental burden, that is, such a compound is decomposed in the environment or in the body, and its decomposition product will accumulate. Accordingly, a release agent composition comprising a fluorocopolymer having structural units based on a monomer having a Rf group having at most 6 carbon atoms and having structural units based on a monomer having a Rf group having at least 8 carbon atoms reduced as far as possible, and which can impart moderate adhesion and releasability, has been desired.